Water heater with programmable low temperature mode

Abstract

The temperature in a water tank (e.g., a residential water tank) is monitored, and a controller switches between a high temperature mode of operation and a low temperature mode of operation (e.g., based on a daily or weekly program). During the low temperature mode of operation, the controller generates signals to selectively activate a water heater to keep the water's temperature within a first range of values, (e.g., between 105 and 113° F). During the high temperature mode of operation, the controller generates signals that cause the water heater to heat the water to a temperature that is above the first range of values. This arrangement may be used for saving energy by operating in the low temperature mode at night and during those parts of the day when nobody is home, and by operating in the high temperature mode in the morning and evening when the demand for hot water is typically high. This arrangement is also well-suited for day-care centers and nursing homes, in which case the low temperature mode is used to reduce the risk of scalding. It is also useful in the homes of people who wish to avoid violating a religious injunction that prohibits heating liquids beyond a threshold temperature on the Sabbath.

1 . A water heating apparatus comprising: 
 a tank for holding a volume of water;    a temperature sensor configured to be in thermal contact with the water and produce an output signal that is accurately indicative of the water's temperature;    means for heating the water in the tank; and    a controller that monitors the water's temperature based on the output signal and selects, based on the passage of time, either a high temperature mode of operation or a low temperature mode of operation,    wherein in the low temperature mode, the controller, based on the output signal, generates signals to selectively activate the means for heating so as to keep the water's temperature within a first range of values, and    wherein, in the high temperature mode, the controller generates signals that cause the means for heating to heat the water to a temperature that is above the first range of values.    
   
   
       2 . The water heating apparatus of  claim 1 , wherein the temperature sensor comprises a thermistor.  
   
   
       3 . The water heating apparatus of  claim 1 , wherein the temperature sensor is implemented in an integrated circuit.  
   
   
       4 . The water heating apparatus of  claim 1 , wherein the means for heating comprises a gas burner, and wherein the controller comprises a gas ignition controller that is operatively connected to the gas burner.  
   
   
       5 . The water heating apparatus of  claim 1 , wherein the tank has a capacity of at least 30 gallons.  
   
   
       6 . The water heating apparatus of  claim 1 , wherein the controller is programmed to cycle between the low temperature mode and the high temperature mode based on the time of day and a user-programmed setting.  
   
   
       7 . The water heating apparatus of  claim 6 , wherein the first range of values has a range of 6° F. or less, and the upper limit of the first range of values is below 113° F.  
   
   
       8 . The water heating apparatus of  claim 7 , wherein the lower limit of the first range of values is at least 105° F.  
   
   
       9 . An apparatus comprising: 
 a temperature sensor configured to be in thermal contact with water in a tank and produce an output signal that is accurately indicative of the water's temperature; and    a controller configured to monitor the water's temperature based on the output signal and select, based on the passage of time, either a high temperature mode of operation or a low temperature mode of operation,    wherein in the low temperature mode, the controller, based on the output signal, generates signals to selectively activate a water heater to keep the water's temperature within a first range of values, and    wherein, in the high temperature mode, the controller generates signals that cause the water heater to heat the water to a temperature that is above the first range of values.    
   
   
       10 . The apparatus of  claim 9 , wherein the temperature sensor comprises a thermistor.  
   
   
       11 . The apparatus of  claim 9 , wherein the temperature sensor is implemented in an integrated circuit.  
   
   
       12 . The apparatus of  claim 9 , wherein the controller is programmed to cycle between the low temperature mode and the high temperature mode based on the time of day and a user-programmed setting.  
   
   
       13 . The apparatus of  claim 12 , wherein the first range of values has a range of 6° F. or less, and the upper limit of the first range of values is below 113° F.  
   
   
       14 . The apparatus of  claim 13 , wherein the lower limit of the first range of values is at least 105° F.  
   
   
       15 . A method of controlling the temperature of water in a tank comprising the steps of: 
 monitoring the temperature of the water in the tank;    switching, based on the passage of time, between a high temperature mode of operation and a low temperature mode of operation;    generating, during the low temperature mode, signals to selectively activate a water heater to keep the water's temperature within a first range of values; and    generating, during the high temperature mode, signals that cause the water heater to heat the water to a temperature that is above the first range of values.    
   
   
       16 . The method of  claim 15 , wherein the switching step comprises switching between the high temperature mode and the low temperature mode based on the time of day and a user-programmed setting.  
   
   
       17 . The method of  claim 16 , wherein the first range of values has a range of 6° F. or less, and the upper limit of the first range of values is below 113° F.  
   
   
       18 . The method of  claim 17 , wherein the lower limit of the first range of values is at least 105° F.  
   
   
       19 . A water heating apparatus comprising: 
 a tank for holding a volume of water;    a temperature sensor configured to be in thermal contact with the water and produce an output signal that is accurately indicative of the water's temperature;    means for heating the water in the tank; and    a controller that monitors the water's temperature based on the output signal and recognizes when the Jewish Sabbath occurs based on the passage of time or receipt of a time-dependent signal,    wherein the controller, based on the output signal, selectively activates the means for heating to keep the water's temperature within a first range of values during the Jewish Sabbath, and wherein the controller controls the means for heating so that water is heated to a temperature that is above the first range of values during at least some other times.    
   
   
       20 . The water heating apparatus of  claim 19 , wherein the first range of values has a range of 6° F. or less, and the upper limit of the first range of values is below 113° F.  
   
   
       21 . The water heating apparatus of  claim 20 , wherein the lower limit of the first range of values is at least 105° F.  
   
   
       22 . The water heating apparatus of  claim 19 , wherein the controller recognizes when Jewish holidays occur based on the passage of time or receipt of a time-dependent signal, and wherein the controller, based on the output signal, selectively activates the means for heating to keep the water's temperature within the first range of values during Jewish holidays.  
   
   
       23 . The water heating apparatus of  claim 22 , wherein the first range of values has a range of 6° F. or less, and the upper limit of the first range of values is below 113° F.  
   
   
       24 . The water heating apparatus of  claim 23 , wherein the lower limit of the first range of values is at least 105° F.  
   
   
       25 . An apparatus comprising: 
 a temperature sensor configured to be in thermal contact with water in a tank and produce an output signal that is accurately indicative of the water's temperature; and    a controller that monitors the water's temperature based on the output signal and recognizes when the Jewish Sabbath occurs based on the passage of time or receipt of a time-dependent signal,    wherein the controller, based on the output signal, selectively activates a water heater to keep the water's temperature within a first range of values during the Jewish Sabbath, and to heat the water to a temperature that is above the first range of values during at least some other times.    
   
   
       26 . The apparatus of  claim 25 , wherein the first range of values has a range of 6° F. or less, and the upper limit of the first range of values is below 113° F.  
   
   
       27 . The apparatus of  claim 26 , wherein the lower limit of the first range of values is at least 105° F.  
   
   
       28 . The apparatus of  claim 25 , wherein the controller recognizes when Jewish holidays occur based on the passage of time or receipt of a time-dependent signal, and wherein the controller, based on the output signal, selectively activates the means for heating to keep the water's temperature within the first range of values during Jewish holidays.  
   
   
       29 . The apparatus of  claim 28 , wherein the first range of values has a range of 6° F. or less, and the upper limit of the first range of values is below 113° F.  
   
   
       30 . The apparatus of  claim 29 , wherein the lower limit of the first range of values is at least 105° F.  
   
   
       31 . A method comprising: 
 accurately sensing the temperature of water in a tank;    recognizing when the Jewish Sabbath occurs; and    selectively activating a water heater to keep the water's temperature within a first range of values during the Jewish Sabbath, and to heat the water to a temperature that is above the first range of values during at least some other times.    
   
   
       32 . The method of  claim 31 , wherein the first range of values has a range of 6° F. or less, and the upper limit of the first range of values is below 113° F.  
   
   
       33 . The method of  claim 32 , wherein the lower limit of the first range of values is at least 105° F.  
   
   
       34 . The method of  claim 31 , further comprising the steps of: 
 recognizing when Jewish holidays occur; and    selectively activating the water heater to keep the water's temperature within the first range of values during the Jewish holidays.    
   
   
       35 . The method of  claim 34 , wherein the first range of values has a range of 6° F. or less, and the upper limit of the first range of values is below 113° F.  
   
   
       36 . The method of  claim 35 , wherein the lower limit of the first range of values is at least 105° F.